Basically high resilience polyurethane foams are produced by the reaction of highly primary hydroxyl-capped, high molecular weight polyols with organic isocyanates and water. High resilience polyurethane foams are distinguishable, in part, from conventional hot cure polyurethane foams by the use of such polyols and the fact that high resilience polyurethane foams require little or no oven curing and thus are often referred to as cold cure foams. Such foams are extremely desirable for cushioning applications because of their excellent physical properties, e.g., very high foam resilience, low flammability, open-celled structure, low flex fatigue (long life) and high SAC factors (load bearing properties).
Because of the high reactivity of high resilience foam ingredients and their rapid buildup of gel strength, sometimes the foam can be obtained without a cell stabilizer. However such foams typically have very irregular cell structure as particularly evidenced by surface voids and the lack of discovery of a proper agent to help control cell structure has been a major problem in the art.
Attempts to solve this problem with surfactants generally employed in the stabilization of hot cure polyurethane foam have not proven satisfactory because such surfactants tend to overstabilize, causing extremely tight, shrinking foam. Nor is the problem corrected by reducing the concentrations of such surfactants, since at concentrations required to eliminate shrinkage, the cells are no longer stabilized satisfactorily and the foam structure becomes irregular, coarse and contains surface voids.
U.S. Pat. No. 4,042,540 discloses that a variety of low viscosity siloxanes, including low viscosity alkoxymodified siloxanes and low viscosity dimethylsilicone oils, are better stabilizers for high resilience polyurethane foams than higher viscosity dimethylsilicone oils. The alkoxy groups in the low viscosity siloxanes preferably contain from one to six (apparently more preferably one to four) carbon atoms. The low viscosity siloxanes contain from four to twelve silicon atoms and contain only very small amounts of siloxane species containing more than twelve silicon atoms (e.g., less than 0.5% by weight). Such higher molecular weight siloxanes can be removed by fractional distillation. There is no suggestion of any particular benefit resulting from the use of any alkoxysilicon composition wherein the alkoxy groups contain from five to eighteen carbon atoms.
Several other patents disclose the use of organosiloxane copolymers as foam stabilizers in high resilience foam formulation. U.S. Pat. No. 3,905,924 relates to the use of cyanoalkylsiloxane copolymers as stabilizers for high resilience polyurethane foam. U.S. Pat. No. 3,741,917 describes siloxane-oxyalkylene copolymers and the use of said organosiloxane copolymers in the formulation of high resilience polyurethane foam. U.S. Pat. No. 3,935,133 teaches the use of high molecular weight silicate esters of polyether alcohols to stabilize high resilience polyurethane foam. U.S. Pat. Application Ser. No. 932,637, filed Aug. 10, 1978, now U.S. Pat. No 4,210,726 discloses a process for producing high resilience polyurethane foam utilizing as a foam stabilizer a combination of an organosiloxane copolymer and a hydrocarbon oil. However, none of the latter mentioned patents or application disclose alkoxysilicon compositions and their use as foam stabilizers in the manufacture of low density high reslience polyurethane foam.
Several other references disclose alkoxysilicon compositions. Alkoxysilane monomer structures such as dimethyldioctoxysilane are described in a reference text entitled "Organosilicon Compounds" by Vladimir Bazant et al., Academic Press, New York and London, 1965, Vol. 2, page 685. U.S. Pat. Application Ser. No. 579,600, filed May 21, 1975, now U.S. Pat. No. 4,261,848 relates to alkoxysiloxanes characterized by alkoxy end-blocking groups derived from alcohols having boiling points and solidification points in particular ranges, and the use of these alkoxysiloxanes as hydraulic fluids. U.S. Pat. No. 2,909,549 teaches a method for making alkoxy-end-blocked silicone polymers such as trialkoxypolysiloxane polymers, and the use of the alkoxy end-blocked silicone polymers as industrial oils, intermediates, dielectric agents and water-repellent agents. However, none of the latter mentioned references disclose the use of alkoxysilicon compositions as foam stabilizers in the manufacture of low density high resilience polyurethane foam.
Within the past few years, cushions fabricated from high resilience polyurethane foam have gained increasingly wide acceptance in automotive seatings. Automotive industry requirements decreased from the foam density needed for seat cushions, thus increasing the difficulty of stabilization of high resilience polyurethane foam. Recently new polymer/polyol systems with high water levels have been proposed which can produce foam cushions with densities of 1.50 to 1.75 lbs./cubic foot and acceptable physical properties in comparison to the commercial foaming systems. However, without any foam stabilizing surfactant, the new polymer/polyol-high water systems produced foams with large and irregular cells or caused collapse of the foam. The addition of commercial high resilience polyurethane foam surfactants (including the low viscosity propoxy-modified siloxanes, the low viscosity dimethylsilicone oils, cyanoalkylsiloxane copolymers and siloxane-oxyalkylene copolymers disclosed in the above-mentioned patents) to this new polymer/polyol-high water system did not correct these problems. The commercial high resilience polyurethane foam surfactants caused collapse of the foams, and commercial flexible "hot-cure" polyurethane surfactants caused severe shrinkage and pneumatic foams. Thus, it is a problem in low density high resilience polyurethane foam formulations to obtain a surfactant which has a proper degree of cell stabilizing ability. This problem is solved by the present invention and also by copending U.S. Application Ser. No. 134,637, filed Mar. 27, 1980, which describes novel alkylmodified siloxane copolymers having beneficial utility as foam stabilizers in the formulation of low density high resilience polyurethane foam.